1. Field of the Invention
The present invention relates to an ink jet recording head for ejecting ink through use of heat energy, and a method of producing the ink jet recording head.
2. Description of the Related Art
Hitherto, an ink jet recording apparatus for ejecting ink to record an image on a recording medium is known. An ink jet recording head for ejecting ink is mounted on the ink jet recording apparatus.
There is an ink jet recording head that includes an ink ejection portion for ejecting an ink droplet through use of heat energy on a substrate. The ink ejection portion includes a heating resistor element for applying heat to supplied ink to provide the ink with an ejection pressure, and a nozzle plate provided with a nozzle for ejecting the ink. A groove is formed in one side surface of the nozzle plate, and the nozzle plate is provided on the substrate so that the one side surface is held in abutment with the substrate. The groove and the substrate form an ink flow path.
The heating resistor element is placed at a position on the substrate where the heating resistor element is capable of applying heat to ink stored in the ink flow path. When the heating resistor element generates heat at a desired timing, the ink stored in the ink flow path is heated. The heated ink is boiled to generate a bubbling pressure, which allows the ink in the ink flow path to be ejected from the nozzle communicating with the ink flow path.
In such an ink jet recording head, the heat generated by the heating resistor element may be transmitted also to the substrate, and the temperature of the substrate may rise.
When the temperature of the substrate rises, the ink in the ink flow path is heated by the heat of the substrate. That is, the ink is heated even in a state in which the heating resistor element does not generate heat, and the ink is boiled more easily. Thus, when the heating resistor element generates heat, the heated ink is ejected in a period of time shorter than that of ink not heated by the substrate. As a result, the ink is ejected at a timing different from a desired timing, which causes a degradation in quality of a recorded image.
Further, the heat of the substrate may be transmitted to the nozzle plate, to thereby change the shape of the nozzle. The deformation of the nozzle may change the size of the ink droplet and an ejection direction thereof, and the ink droplet landing point deviates from a desired position to cause a degradation in quality of a recorded image.
Accordingly, Japanese Patent Application Laid-Open No. H04-144157 discloses a structure in which a heat radiation member for releasing heat of a substrate is provided on the substrate. By releasing the heat of the substrate through the heat radiation member, an increase in temperature of the substrate can be suppressed, and hence the heating of ink by the substrate and the deformation of the nozzle can be suppressed. As a result, the degradation in quality of a recorded image can be suppressed.
However, in recent years, there has been a demand for an ink jet recording head capable of recording an image with higher quality at a higher speed.
In order to enhance image quality, an increase in density of the nozzle is effective, and along with this, it has been proposed that the heating resistor elements be placed on the substrate at a higher density. Therefore, in such an ink jet recording head, a greater amount of heat can be transmitted to the substrate more easily.
Further, in order to record an image at a higher speed, it has been proposed that the interval between timings for the heating resistor elements to generate heat be shortened. In this case, the amount of the heat generated by the heating resistor elements per unit time becomes larger.
By increasing the density of the arrangement of the heating resistor elements and shortening the interval between the timings for the heating resistor elements to generate heat, in the structure disclosed by Japanese Patent Application Laid-Open No. H04-144157, the amount of the heat transmitted from the heating resistor elements to the substrate may become larger than that transmitted from the substrate to the heat radiation member in some cases. As a result, the heat of the substrate may not be released sufficiently, and the temperature of the substrate may rise, to thereby degrade recording quality.